Journal of Archaeological Science (1998) 25, 985–1000Article No. as970282

Tortoise Remains from a Later Stone Age Rock Shelter in theUpper Karoo, South Africa

C. Garth Sampson

Department of Anthropology, Southern Methodist University, Dallas, Texas 75275-0336, U.S.A. andHuman Sciences Division, South African Museum, P.O. Box 61, Cape Town 8000, South Africa

(Received 2 December 1997, revised manuscript accepted 22 January 1998)

The upper Karoo of central South Africa is a semi-desert region supporting several species of chelonia, and culturaldeposits in local rock shelters also yield abundant tortoise bones. In the Late Holocene fill of Haaskraal rock shelter,remains of at least four kinds of tortoise and a terrapin have been identified. However, there is an anomalous absenceof the giant adult form of Geochelone pardalis, which is highly visible in the modern fauna. Frequencies of the twodominant species Homopus femoralis and H. boulengeri do not vary during the two millennia of accumulation, in spiteof the major changes in veld cover reported in local pollen and micromammal records. Instead, changes in tortoise sizeand skeletal composition reflect increasing admixture of remains derived from non-human predators, as occupation byhumans dwindled during historical times. Comparisons with other rock shelter samples are needed, but investigationsof tortoise remains from modern raptor nests and killing grounds are also an urgent priority. ? 1998 Academic Press

Keywords: TORTOISES, TAPHONOMY, RAPTORS, HOLOCENE, LATER STONE AGE, KAROO,SOUTH AFRICA.

Introduction

M any Holocene and some Upper Pleistocenesites in South Africa yield abundant tortoiseremains, but few of the latter have received

detailed archaeozoological analysis. An exception isthe angulate tortoise Chersina angulata, common insites of the southwestern Cape coastal region, where itis the dominant species found in archaeological assem-blages. However, it is often prey to raptorial birds inthe modern fauna (Branch, 1984; Avery et al., 1985;Boshoff, Palmer & Avery, 1990; Boshoff et al., 1991),thus its archaeological trace may not reflect onlyhuman predation. C. angulata remains have beenintensively studied, particularly the humerus whichprovides MNI counts and metric data (Klein &Cruz-Uribe, 1983, 1987, 1989; Cruz-Uribe & Schrire,1991). Spatial distribution of the skeleton, carapaceand plastron have been studied in the Dunefield Mid-den site (Parkington et al., 1992) where the highestMNI counts were obtained from the entoplastronrather than the humerus (P. Nilssen, pers. comm.). Insome sites the sheer volume of highly fragmentedtortoise bone precluded the counting of all elements(G. Avery, pers. comm.), but this paper demonstratesthe need for more comprehensive analysis.

In the adjacent eastern Cape region, Holoceneshelters produce more diverse tortoise assemblages,reflecting the differences in this habitat. C. angulata is

9850305–4403/98/100985+16 $30.00/0

present, but remains of the leopard (mountain) tortoiseGeochelone pardalis, the areolate padloper Homopusareolatus, the tent tortoise Psammobates tentorius,and the terrapin Pelomedusa subrufa also occur(Leslie-Brooker, 1987; Hall, 1990).

Sites in the South African interior have not receivedcomparable treatment, but are potentially of greatinterest because the modern tortoise fauna is sodiverse. Of particular note is the semi-desert upperKaroo region with eight different taxa, probably thehighest tortoise diversity worldwide (Greig, 1979). Onthe extreme northern limits of the ranges of C. angulataand H. areolatus, the upper Karoo also supports theother three species already mentioned, plus three moreendemic taxa. It is possible, therefore, that past cli-matic fluctuations may have shrunk or expanded theranges of some of these taxa. It follows that stratifiedtortoise remains from archaeological sites may serve asproxy evidence of past rainfall regimes, and also ofhistorical disruptions to the veld cover by humans.This approach has been applied to much scarcerassemblages of owl-deposited micromammals fromupper Karoo shelters and caves (Avery, 1991).

However, tortoise remains in Karoo shelters arepotentially mixtures of food refuse left by humans andby non-human predators, particularly raptors whichprey regularly on tortoises. Although no systematicfield observations have been published, tortoise boneconcentrations at ‘‘killing rocks’’ (Greig, 1979) occur

? 1998 Academic Press

986 C. G. Sampson

commonly at certain boulders or promontories whereraptors (especially crows and ravens) habitually droplarger tortoises from great heights in order to smashopen the shell. Crows and ravens can also smash opensmall tortoise shells with their heavy beaks (Hewitt,1937; Greig, 1979). Roosts and feeding perches are at apremium in this treeless environment, so that anysuitable rock ledge is heavily used by a wide variety ofraptors for this purpose. Larger ledges support perma-nent nests occupied seasonally by many different largebirds. Two local rock shelters support such nests,although Haaskraal has none. Also, the author hasdisturbed a kite- or shrike-size raptor at rest on thefloor of a small rock shelter, although no other recordsof floor-roosting have been found. Consequently,changes in tortoise species during the accumulation ofsuch fills could also be influenced by the mix of raptorversus human occupation at different levels, andthis factor should be eliminated before climaticimplications or human impacts on vegetation can beconsidered.

While records of small carnivores taking tortoisesexist (e.g. Hewitt, 1937) no systematic studies areknown. In the past, at least 10 species of small carni-vore occurred in this habitat (Plug & Sampson, 1996),of which Hewitt (1937) mentions badgers and jackalsas habitual predators of tortoises. Many other smallcarnivores could have eaten tortoises and most of themwould have been temporary visitors to rock shelterswhen no humans were present.

With these questions in mind, the tortoise remainsfrom a small rock shelter in the upper Seacow Rivervalley, in the heart of the upper Karoo (Figure 1), wereanalysed to discover the degree to which non-humanand human contributors can be identified. Haaskraal

Shelter is a modest overhang in the side of a doleriteridge (Figure 2) about 1·5 km west of the Zoetvleichannel, a tributary of the upper Seacow River drain-age. It has no obvious perching ledges on its slopingrear wall and roof, nor is the top of the roof’s rimsuitable for nesting since it is fully exposed to theelements.

The surrounding terrain is typical semi-arid scrubdesert with summer grasses, today used mainly forextensive sheep farming. In the 19th century very largeherds of game still flourished here (Neville, 1996),thanks to a nutritious Karoo vegetation and theregion’s many reliable water points. Tortoises stillabound in this veld today, becoming more activebefore (infrequent) rainstorms. The giant G. pardalis isespecially conspicuous, commonly seen near waterpoints.

Cultural stratigraphy and datingTortoise remains also abound in the shelter’s 70 cmdeep deposit, where they occur with densely packedlithic artefacts (Pease, 1993), bone arrowhead frag-ments and ostrich eggshell beads (Hart, 1989), pot-sherds (Bollong, 1996), ostrich eggshell fragments(Sampson, 1994), mammal remains (Plug & Sampson,1996), micromammals, birds, fish, freshwater musselsand amphibians (Sampson, in press).

During the excavation of several square metres of fillunder the overhang (Figure 2), no clear stratigraphicalbreaks were visible in the dark, silty deposit. Conse-quently it was removed in thin, arbitrary spits, withtight horizontal recording which allows any recovereditem to be plotted to the nearest 25#25 cm area andthe nearest 2–3 cm depth.

Homopus femoralis

Haaskraal shelter

0 500

km

Homopus

Boulengeri

Figure 1. Map of South Africa, showing the location of Haaskraal Shelter and the modern distributions of the two most common tortoisesfound in its deposits.

Tortoise Remains from a Later Stone Age Rock Shelter 987

Directly dated ceramic markers have been used tocorrelate several local shelter deposits into five ceramic‘‘phases’’ (Bollong & Sampson, 1996) and all, exceptPhase 3, can be identified in the Haaskraal sequence.Thus each small excavated unit can be attributed to aphase and a cultural stratigraphy has been delineatedwithin the matrix of arbitrary spits and small blocks.Rock-filled talus, totalling 4 m2, excavated near thelow retaining wall of a prehistoric stock enclosure builtoutside the shelter, are correlated with the depositunder the overhang by the same ceramic markers. Thesequence is as follows:

Phase 0 (Preceramic) lies on bedrock, with a basalcharcoal date of 1850&45 .

Phase 1 is characterized by rare Khoi ware andundecorated fibre-tempered sherds. Two charcoaldates of 1180&70 and 1140&60 come from thislevel. It is followed by a gap of some 500 years.

Phase 2 contains the lowermost decorated fibre-tempered sherds and livestock remains. These itemsappear at Haaskraal at the end of this phase, whichdates earlier elsewhere. Dates are 544&43 oncharcoal, 515&65 on cattle dentition, and 410&65 on sheep bone (Plug et al., 1994). There may havebeen another hiatus while Phase 3 accumulated inother local shelters, or Phase 3 may be merged herewith (lower) Phase 4 for want of enough ceramicmarkers.

Phase 4 (possibly 3 and 4) is demarcated by thepresence of stamp-impressed decorations on the fibre-tempered sherds. Khoi pottery and livestock disappearfrom the sequence. No dates are available from this

relatively thick, bone-rich horizon, but direct dates onpottery with these decorations (Sampson & Vogel,1995) bracket the phase to c. 300–200 . Phase 4 thusrepresents the century before the arrival of the firstEuropeans in the upper Seacow valley.

Phase 5a is characterized by the first appearance ofEuropean items, mainly glass trade beads (Saitowitz &Sampson, 1992) and novel varieties of livestock (Voigt,Plug & Sampson, 1995). These cannot be dated withany precision, but probably belong to the last quarterof the 18th century and the first quarter of the 19thcentury. A stone wall was built up to the drip line ofthe overhang at this time.

Phase 5b is an arbitrary subdivision of the Post-Contact (historical) levels and includes the uppermostspits and rare surface material. There is a widespreadthinning out of tortoise remains between Phase 5a and5b, and this plane was followed when subdividing thedeposit. Phase 5b contains glass trade beads of mid-19th century date. There is also a lead bullet dating tothe later 1850s (Westbury & Sampson, 1993), but it islikely that occupation continued into at least the thirdquarter of the 19th century, since bleached faunalremains still covered the surface of the deposit behindthe (now collapsed) stone wall. There is a scattering offresh tortoise material across the surface and in theinterstices of the collapsed wall.

A few small disturbed areas have been pinpointed inthe deposits. Parts of a refitted Phase 5 cooking bowlwere thrust down into Phase 4 at the back of thedeposit (Bollong, 1994), probably caused by the burialof sheep bones by stock thieves or by burrowing

Dolerit

e

N

Wall

AB

EF

G

I

J

Drip lin

e

0 1

m

Figure 2. Plan of excavations at Haaskraal Shelter, after Hart (1989).

988 C. G. Sampson

amphibians, the unweathered bones of which are alsofound here at depth. This disturbance has brought acluster of backed microliths up into the historicalPhase 5 levels (Close & Sampson, in press). Other smalldisturbances can be pinpointed further forward in theshelter by the presence of unweathered amphibianremains at depth, again with backed microliths imme-diately overlying the areas of these burrow deaths.Presumably a few older tortoise remains have migratedupwards into Phase 5 near these small disturbances,but they cannot be recognized.

Occupational history and identitiesHaaskraal was first occupied in about 200 by LaterStone Age hunter–gatherers whose lithic technologyresembles the developed interior Wilton industry. Theywere here intermittently until about 900 when theyacquired ceramics. Haaskraal seems to have fallen intodisuse for about 500 years and was reoccupied soonafter 1400, possibly by prehistoric herders whosepottery links them to ancestral Khoikhoi (Bollong,Sampson & Smith, 1997) or by hunter–gatherers inregular contact with those herders. Although signs ofprehistoric herding disappear from Haaskraal ataround 1700, and possibly from the entire upperSeacow valley (Sampson, 1996), the shelter continuedto be in use by hunter–gatherers up to and after thearrival of the Europeans, who called these indigenes‘‘Bushmen’’.

Habitation continued over most of the 19th centuryby Bushmen farm servants and/or vagrants and stockthieves (Sampson, 1995), during which time gameremains accumulated in the fill at much faster rates.This probably reflects the periodic presence of fullyarmed shepherds and stockmen at a veepos (stockpost), the ruins of which stand at the foot of theHaaskraal talus slope. Declining game numbers mayhave led to rapidly increasing consumption of ostricheggs. Although rich in fauna, these historic levels alsocontain hints of discontinuous and dwindling humanoccupation. Changes in the composition of the veryabundant amphibian remains suggest increasing useof the shelter floor by raptorial birds and/or smallcarnivores, as the humans’ presence diminished.

The tortoise remains can be reasonably expected toreflect some of these events and they could provideindependent tests of the interpretations briefly outlinedhere. Tortoises may have been taken in greater num-bers as the game supply ran out, then tortoise remainsmay have been brought in by raptors/small carnivoresrather than by Bushmen at the end of the sequence.Raptors/small carnivores may also have contributedmore material during the hiatus between Phases 1–2.

MethodsRecovery

Following excavation, the vertebrate fauna from eachsmall unit was separated from the artefacts and shell

remains. The fauna was then processed by a mamm-alogist who set aside whole and readily identifiabletortoise remains as they were encountered while iden-tifying the mammals. Some 77% of the tortoise remainswere removed an this stage. The author undertook asecond and third sweep of the residual fragments andrecovered another 23%, comprising mostly brokenand/or burned tortoise parts.

Modern tortoise distributionsThe literature was searched for modern species distri-butions which include the upper Seacow River valley.Recent distribution summaries (Newberry & Jacobsen,1986; Boycott & Borquin, 1988) depend mainly ondata from Greig & Burdett (1976) which has quiteadequate sample coverage for the upper Karoo region.More recent supplementary surveys (Branch & Braack,1987; Branch, 1990) have not substantially altered thepicture for the Seacow valley.

Haaskraal Shelter is located outside the modernnorth limit of C. angulata. It is on the western rim ofthe recorded range of G. pardalis; and probably beyondthe northern limit of H. areolatus. It is on the northeastboundary of the recorded range of the Karoo(grooved) padloper H. boulengeri, but is well within theknown range of the greater padloper H. femoralis(Figure 1). It is inside the northeastern boundary of thedistribution of the southern tent tortoise P. tentoriustentorius; and on, or just within the southern limit ofthe northern tent tortoise P. tentorius verroxii. The siteis also within the range of the almost ubiquitous Capeterrapin Pelomedusa subrufa.

Reference material and identificationsNo systematic osteological atlas (e.g. Gaffney, 1979;Sobolik & Steele, 1996) exists for the South Africantortoises, and this paper does not describe detailedcriteria for identification. The identity of eachHaaskraal element is a best fit with the equivalentelement of one of the reference specimens availableto the author: C. angulata (large and medium-sizedspecimens); G. pardalis (giant, large and small); H.areolatus (medium); H. boulengeri (large, medium andsmall); H. femoralis (two medium and one small); P.tentorius tentorius (medium); P. t. verroxii (medium);and P. subrufa (large and medium). Most of these werecomplete and fully disarticulated specimens, with thefollowing exceptions: limbs of the adult C. angulatawere incomplete. Also the shell of the adult G. pardaliswas not disarticulated. However, no excavated ele-ments remotely resembled this giant form, so thatfurther detail was unneeded. The large H. boulengeriwas the nearly complete front half (45 elements) of aspecimen from Phase 4 levels in Haaskraal itself. Noreference material for the hindquarters and rear cara-pace plates were available. The medium specimenlacked all skeletal parts, and the small category

Tortoise Remains from a Later Stone Age Rock Shelter 989

included only the right side of the skeleton, dissectedfrom a fresh specimen. The small H. femoralis speci-men was an incomplete portion (28 elements) found inthe interstices of the collapsed stone wall in Phase 5.The large P. subrufa was a mounted display specimen,but this again proved to be no handicap since nothingof this size was present in the excavated material.

The terminology of Greig (1979) was used to labelthe bones of the plastron and carapace. Among thelatter, neurals (n) are the equivalent of vertebrals ofother authorities, and costals (c) are called pleurals inother sources. Lefts and rights were identified, andcarapace bones were numbered sequentially fromanterior to posterior. Thus m4 is the fourth marginalfrom the nuchal. The term ‘‘skeletals’’ will be used hereto designate all non-shell elements of the skeleton.

Overall, identification of the carapace was the leastambiguous, particularly between the numericallydominant H. boulengeri and H. femoralis. The shortageof reference material made it impossible to discriminatewith confidence between the subspecies of Psammo-bates tentorius, and there are residual doubts about thepossible overlap in morphology between some parts ofthe P. t. verroxii and H. femoralis carapace.

Identity of the plastron was possible only withreasonably complete elements and the problem ofwithin-species variability hangs over the identities ofthe better-preserved, smaller and tougher bones.

The relatively scarce cranial and axial parts were notidentified to taxon. Of the postcranial skeletals, Hall(1990) has pointed out that the relatively abundanthumeri cannot be identified to taxon, although thereference material used in this project allowed quiteconsistent separation of Homopus from Psammobates,the latter having more laterally bowed shafts. Otherlimb bones could be separated only on the basis of sizerather than morphology. Of the pectoral and pelvicbones, the latter were more diagnostic of species,especially if reasonably complete.

Size estimatesExcept G. pardalis, which can weigh up to 10–20 kg,most of these tortoises are quite small. Adult H.boulengeri has a weight range of only 70–110 g and is a

mere 9–10 cm long, while H. femoralis grows to 350–600 g, and P. t. tentorius to 150–260 g (Boycott &Bourquin, 1988).

Estimates of relative element size used in this studyare wholly subjective and judged by eye in relation tothe sizes of the available reference specimens whichwere deemed ‘‘medium’’ etc. in relation to the otherreference specimens of the same species. Where poss-ible, individual fragments were assigned as large,medium, medium–small, small and very small. Manylimb bones can be classified only as Homopus spp. andtheir sizes were coded as small/medium and small/verysmall.

Following Klein & Cruz-Uribe (1983, 1987),humeral distal width was recorded with digital callipersto the nearest 0·01 mm.

Details and provenience of each element wereentered in a database and sorted to acquire the variouscombinations described below. Some elements fromthe surface of the shelter floor were classified as fresh,and excluded from Phase 5b on the grounds of appear-ance. Included among these were some chitinous scutesof H. femoralis, plus some intrusive material from thedisturbed areas described above. These are of specialinterest because they must have accumulated afterthe shelter was abandoned by humans, and reflectrelatively unmixed non-human agents.

ResultsThe two endemic species of Homopus dominatethroughout the sequence with only rare occurrences ofG. pardalis and P. tentorius (Table 1). The singlemarginal of H. areolatus is a very tentative ascription,unlike that of P. subrufa, which is unambiguous. Noelements could be ascribed to C. angulata. Much of theunidentifiable material is highly fragmented and/orburned. NISP counts of diagnostic pieces per phase arelarge enough to permit percentage calculations, whichreveal an apparent steady decline in the frequency ofH. boulengeri with parallel gains in H. femoralis(Figure 3). However, this trend disappears when thevalues are converted to MNI counts (Table 2), suggest-ing that it must be an artefact of the sorting procedure,

Table 1. NISP counts of tortoise remains by taxon and phase

PhaseGeochelone

pardalisHomopusareolatus

Homopusboulengeri

Homopusfemoralis

Homopussp. indet.

Psammobatestentorius

Pelomedusasubrufa

Speciesindet. Totals

Fresh — — 6 48 13 1 — 7 755b 1 — 24 109 43 1 — 36 2145a 3 — 17 107 21 — — 45 1934 5 1 86 191 14 6 — 75 3782 2 — 52 132 11 6 1 104 3081 — — 24 51 2 — — 59 1360 1 — 14 20 1 — — 34 70

Totals 12 1 223 658 105 14 1 360 1374

990 C. G. Sampson

rather than a real shift in the processes of tortoisedeposition at Haaskraal. The element on which MNIcounts were based varied widely from one phase, taxonand size category to the next. For the entire collectionthe right m1 plate of the carapace was the mostnumerous (N=37).

Classification of Homopus limb bonesThe frequency of all skeletal elements increases steadilythrough the sequence, with complementary declines inthe proportion of carapace and plastron (Figure 4).Because the limb bones of adult H. boulengeri cannotbe distinguished with confidence from those of juvenileH. femoralis, they must be placed in the catch-allcategory of Homopus spp. (see Methods above). Thesame fate befalls limb bones of small H. boulengeriwhich cannot be distinguished from very small H.

femoralis. This means that all H. boulengeri limbs,except the very small class, are not counted into thattaxon. By contrast, medium-sized H. femoralis limbsare outside the upper range of, and cannot be confusedwith H. boulengeri, and are retained in their taxon.Only the (less numerous) small H. femoralis limbs mustbe moved to the Homopus spp. category. As the overallproportion of skeletal elements increases through thesequence, so a growing frequency of H. boulengeri limbbones are ‘‘lost’’ to the Homopus spp. category (Figure5). Although small H. femoralis are also transferred,they must be relatively fewer. Thus the apparentdecline in H. boulengeri NISP seen in Figure 3 resultsfrom the imperfect identification of increasing numbersof limb bones through the sequence. Consequentlythere are no demonstrable changes in the proportionsof tortoise species being deposited throughout thesequence.

100

Fresh

0

0Percentage

Ph

ase

1

5b

5a

4

2

20 40 60 80

55

35

75

135

127

289

193

Homopusboulengeri

G. pardalis

Homopus femoralis

P. tentorius

NIS

P

Figure 3. Cumulative percentages of all tortoise elements (NISP)through Phases 0–5b, and the surface (fresh) sample.

100

Fresh

0

0Percentage

Ph

ase

1

5b

5a

4

2

20 40 60 80

75

70

136

214

193

378

308Carapace

Skeletals

Plastron

NIS

P

Figure 4. Cumulative percentages of all carapace, plastron andskeletal elements through Phases 0–5b and fresh.

Table 2. MNI counts of tortoise remains by phase and species

PhaseGeochelone

pardalisHomopusareolatus

Homopusboulengeri

Homopusfemoralis

Psammobatestentorius

Pelomedusasubrufa Totals

Fresh — — 2 6 1 — 95b 1 — 6 10 1 — 185a 2 — 4 9 — — 154 1 1 8 13 3 — 262 1 — 8 12 2 1 241 — — 4 6 — — 100 — — 2 5 — — 7

Totals 5 1 34 61 7 1 109

Tortoise Remains from a Later Stone Age Rock Shelter 991

FragmentationThe next question is why skeletal elements increaseupwards through the sequence. One possibility is thatthe skeletals are more prone than the shell to break upafter burial, and thus diminish with age. If so, thenskeletals should be more fragmented than the rest.Indeed, only 24·0% of all skeletals are still whole,compared to 35·5% whole carapace elements. How-ever, the plastron is even more fragmented (16·8%intact) than the skeletals, which does not fit the expec-tations of a simple age/attrition model. Other pressuresmust have operated on the plastron besides burialattrition.

When percentages of whole elements are plotted byphase for skeletals and shell (Figure 6), the frequencyof breakage for both shell and skeletals increases withdepth/age, but at unequal (and uneven) rates. Whenpercentages of whole skeletals were plotted separatelyagainst percentages of whole carapace by phase, andagainst percentage of whole plastron by phase, thesame result was obtained. Thus the assumption thatthe skeletals break up progressively faster after burialthan the shell is not supported, and some other causemust be sought to explain the rising frequency ofskeletal parts seen in Figure 4.

Although the numerically dominant H. femoralisgrows to about twice the size of an adult H. boulengeriit does not follow that the elements of this largertortoise are more resistant to taphonomic stress.Apparently, it may be more vulnerable since 39·9% ofrecognizable H. femoralis elements (N=658) are still

complete, compared to H. boulengeri (N=223) ofwhich 47·7% are still whole. But those skeletals of H.boulengeri which were ‘‘lost’’ to Homopus spp. includeonly 19·3% of whole elements and it is probably theremoval of these which has artificially inflated thepercentage of whole elements of the smaller tortoise.Thus its bones are not necessarily tougher. A compari-son of the two taxa by phase is not possible because oflow sample size for H. boulengeri.

Identifiables, fragmentation and skeletal elementsThe effects of burial attrition and burning on thesample are summarized in Figure 7. Frequencies of alldiagnostic elements (all except species indet. in Table 1)increase upwards through the sequence in near-perfectstratigraphical order. This covaries with increasingfrequencies of identifiables, although their relationshipis not perfectly sequential. This is because the Phase 0sample is more charred (27%) than Phases 1 and 2(each 20% charred), and because Phase 4 (14·6%charred) and Phase 5a (12·4% charred) are both lessburned than Phase 5b (20% charred). Nonetheless, theolder Phases 0–2 group separates convincingly fromthe overlying Phases 4–5b. Thus it is mainly theincreasing fragmentation with age/depth that deter-mines how much material will be identifiable, while thedegree of charring is a secondary, although significantfactor. The fresh (non-human) sample contains mark-edly more whole elements than the underlying Phases

100

Fresh

0

0Percentage

Ph

ase

1

5b

5a

4

2

20 40 60 80

33

3

10

107

57

72

26H. femoralis

Homopussp. indet

H.boulengeri

Skeletal N

ISP

Figure 5. Cumulative percentages of skeletals only for Homopus spp.through Phases 0–5b and fresh.

60

50

10

0

Percentage whole skeletals

Per

cen

tage

wh

ole

shel

l ele

men

ts

40

50

30

20

10 20 30 40

0

1

2

5b

5a

4

Fresh

+

+

+

+

Figure 6. Although the survival rates of whole shell parts and wholeskeletals increase with time, the rates are not similar (straight line).With time, shell accelerates over skeletal survival, but not in perfectstratigraphical order.

992 C. G. Sampson

4–5b. Not only has it suffered less age-attrition (and noburning), but it was also spared the intense tramplingand scuffing to which the archaeological samples musthave been subjected. However, this enhanced quota ofwhole elements in the fresh sample has not significantlyincreased its component of identifiables. Some otherfactor must have contributed to its formation.

The proportion of skeletal elements in the samplecould contribute to the proportion of identifiables. Inspite of the difficulties mentioned above, the skeletalparts produced only 5·7% unidentifiable (at least togenus), compared to 9·2% for plastron and 18·6% forcarapace. As skeletal element frequencies increase up-wards through the stratigraphical sequence, they couldenhance the number of diagnostic elements per sample.Figure 8 shows an orderly increase from Phase 0 up toPhase 4, but thereafter the rapid rise in the proportionof skeletal elements has no further effect on the ratio ofidentifiables. Once the skeletal parts rise above aboutone-third of the sample (Phase 5a), there are no furthersignificant gains in identifiables. The most economicalinterpretation is that normal burial attrition is operat-ing independently on both the frequency of skeletalparts and of identifiables up to Phase 4. Thereafter,another factor has intervened in the depositionalprocess.

SizeBones of young tortoise must be more vulnerable toburial attrition and burning than their older, larger and

thicker counterparts. All things being equal, the fre-quencies of small and very small elements shouldincrease up through the sequence. But Figure 9 showsa gradual decrease in the proportion of small and verysmall (juvenile) elements up to Phase 5b, and someother process besides burial attrition, assisted byburning, must be sought to explain this.

Non-human versus human detritusThe gradual decline in juveniles in Figure 9 is disruptedby the fresh, unburned (non-human) sample whichcontains a markedly higher proportion of very smalltortoise bones than any of the archaeological samples.Also, mean widths of humerus distals do not varymuch between Phase 2 and Phase 5b (6·12 mm to6·53 mm), but the fresh (non-human) sample mean isnotably smaller at 5·02 mm. Overall, the largest ele-ment is 8·2 mm and the smallest is 2·9 mm. Unfortu-nately the sample sizes are too small for statisticaltesting.

The fresh sample also stands apart from the rest inits very high proportion of skeletal elements. Whenfrequencies of small and very small elements are plot-ted against the frequency of skeletal material (Figure10), a near-perfect sequential ordering of the samplesemerges, with the fresh sample now totally isolatedfrom the archaeological ones. Evidently non-humandetritus can be distinguished from human foodwasteby its unusually high frequencies of skeletal parts, mostof which are from very small tortoises.

50

100

0

0

Percentage of elements identifiable to taxon

Per

cen

tage

wh

ole

elem

ents

30

40

20

10

20 40 60 80

0

1

Fresh

+

+

+

+

+

2

5b

5a

4

Figure 7. Survival of all whole tortoise elements and proportions ofidentifiables both increase with time, but not at equal rates (straightline), nor in perfect stratigraphical order.

50

100

0

0

Percentage of elements identifiable to taxonP

erce

nta

ge s

kele

tal e

lem

ents

30

40

20

10

20 40 60 80

0

1

Fresh

2

5b

5a

4

Figure 8. Survival rates of skeletals increase in linear order withpercentages of identifiables through the prehistoric Phases 0–4, butthe relationship changes in the overlying (historical) levels.

Tortoise Remains from a Later Stone Age Rock Shelter 993

Herein lies the most promising clue to the thirdfactor, besides normal burial attrition and burning,that contributes to the rapid increase in skeletal parts

up through the sequence (Figure 4). Non-humanagents contributed increasing amounts of tortoise tothe deposit in historical times, but the very smallcomponents were most rapidly destroyed after burial,leaving mostly adult and subadult elements.

Spatial analysisIf non-human detritus made an increasing contributionto the shelter fill with time, this should be visible in thespatial distribution of tortoise bones. The few survivingsmall and very small tortoises resulting from humanfoodwaste should be concentrated in the mammal bonemiddens, those from non-human detritus should bemostly apart from the middens and should includemost of the very small skeletal elements. The latterpattern should become more pronounced up throughthe sequence.

Changes in the distribution of tortoise remains byphase are shown in Figure 11 and the configuration ofthe bone midden in each phase is given in Figure 12. InPhase 0, the tortoise is entirely concentrated in thesmall patches of mammal bone, and this includes thevery small elements.

In Phase 1 tortoise is again concentrated in thearc-shaped bone midden around the rim of the mainhearth. There are a few thin, isolated patches oftortoise around the midden edge, including four smallelements.

In Phase 2 the bone midden is larger, with threeadjacent nodes. Tortoise is concentrated in only one ofthese nodes, with dense patches of tortoise around theedges of the other nodes. For the first time, there aretwo thin patches of tortoise bone well clear of the bonemidden, but these contain no small elements. All thejuveniles are associated with the bone midden.

In Phase 4 the bone midden is at its greatest extentand density. Tortoise bones again tend to concentratearound the edge of this midden, but there is now a veryextensive, thin scatter well beyond the bone midden,with three small patchy concentrations at the back ofthe shelter. Most of the small skeletal elements areoutside the bone midden.

The Phase 5a tortoise is no longer concentrated onthe edges of the bone midden, which is itself becomingmore widespread and patchy. The number and densityof tortoise bone patches beyond the midden is increas-ing to the point where the tortoise may be contributinglocally to the overall bone weight per unit. By now,most of the small elements, especially skeletal elements,are from outside the bone midden.

By Phase 5b the bone midden has broken up intodispersed patches, with tortoise concentrated in onlyone of them. Most of the tortoise remains are thinlyscattered between the bone patches, especially thesmall elements, of which several are very small skeletalelements.

Overall, the changes in patterning fit well with theexpectations of a model in which non-human agents

100

Fresh

0

0Percentage

Ph

ase

1

5b

5a

4

2

20 40 60 80

70

41

87

185

151

313

214

Smalland s/vs

NIS

PMedium, m-s,and m/s

Large

Verysmall

Figure 9. Frequencies of tortoise elements by approximate growthstages through Phases 0–5b and fresh (non-human agent).

50

60

0

10

Percentage small and very small

Per

cen

tage

ske

leta

l ele

men

ts

30

40

20

10

20 30 40 50

01

Fresh

2

5b

5a

4

Figure 10. Percentage of skeletals plotted against percentage ofsmall and very small specimens. The fresh (raptor) sample is isolatedfrom the rest.

994 C. G. Sampson

contribute increasing amounts of tortoise to thedeposit with time.

Evenly distributed damageSystematic processing of the tortoise carcass could giverise to patterns of bone damage concentrated atspecific elements of the shell. If so, then those elementsshould include fewer intact elements than the rest.Counts of fully diagnostic carapace elements, i.e. thoseattributable to specific places on the shell, are almostall too small to allow frequency calculations of wholeversus broken per element. This is possible, however,when they are grouped in left marginals, left costals,etc. Table 3(a) gives the sample totals and frequenciesfrom the left to the right side of the carapace. Neitherside betrays significantly higher rates of breakage thanthe other. Since neurals are almost impossible toidentify to correct position unless they are whole, veryfew broken elements appear in this sample, hence theirinflated frequency.

In Table 3(b) carapace elements are grouped fromfront to back of the shell. On average, the number ofpieces per element declines rearward, although the rearhas more whole pieces than the rest.

Fully diagnostic plastron elements are likewisescarce, and similar groupings are necessary to increasesample size. Table 4(a) shows slightly more damage on

the right side, but there is significantly more damage atthe rear, which has fewer whole pieces (Table 4(b)).

The skeletal elements must also be grouped toincrease sample size. Table 5(a) reveals the verymarked shortage of cranial and axial remains in thissample, 60% of which come from historical layers, i.e.Phase 5a or later. Although limb bones outnumbershoulder and pelvic elements, the latter are notably lessfragmented. Hindlimbs also retain significantly fewerwhole elements than forelimbs. The left side of theskeleton has suffered more damage than the right(Table 5(b)).

Overall, more diagnostic elements and more wholeelements are retained at the front of the carcass than atthe back, but this cannot be construed as systematicprocessing damage. It is just as likely to be the result ofuneven burial attrition across the skeleton.

There is one possible cut mark on the shaft of a rightproximal tibia fragment of a medium H. femoralis inPhase 1. Another possible cut mark occurs on theinside of a c3/5/7 fragment of H. femoralis in Phase 2.

Evenly distributed charringCharred elements are usually attributed to humanfoodwaste. If non-human agents contributed increas-ing amounts of tortoise with time, then the frequencyof burnt tortoise should gradually decrease up through

1–4

5–9

No. of tortoise elementsper c. 1500 cc of matrix

Phase 0 Phase 1 Phase 2

10–14

Phase 4 Phase 5a Phase 5b

15+

1 m

Figure 11. Distribution of all tortoise remains by phase, showing densities per 25#25 cm area. See Figure 2 for whole shelter layout.

Tortoise Remains from a Later Stone Age Rock Shelter 995

the sequence. Altogether 17·6% of the buried materialis charred, and frequencies do indeed decline upwards,there is an anomalous increase in charring at the end ofthe sequence in Phase 5b (Figure 13). When thecharred elements in Phase 5b are plotted in relation tocharcoal density, they are scattered around the singlehearth (Figure 14). However, the small elements are onthe periphery, and some may be non-human detritusburned by accident. This may also explain the overall

increase in charring in Phase 5b. On the other hand,there is no reason why people would not also eat smalltortoises, and this may have been forced upon themif other food sources became scarce and their owntortoise predation increased.

The distribution of charred elements across theshell and skeletals is also of interest. On the carapace,the frequency of charring is very evenly distributedfrom the left to right side, with trivial differences in

Phase 0Weight of all fauna per

c. 1500 cc of matrix1–25 g25–50 g50–75 g

Small or very smalltortoise element

Phase 1 Phase 2

75–100 g

Skeletal element100–150 g

Phase 4 Phase 5a Phase 5b

125–250 g

1 m

Figure 12. Distribution of the bone middens by phase, showing mass fauna weights per 25#25 cm area. Small/very small tortoise remains areincreasingly outside the bone mass from Phase 4 upwards.

Table 3(a). Left to right distribution of fully diagnostic carapace elements, showing frequencies of whole and burntspecimens in each group

Leftmarginals

Leftcostals Neurals

Rightcostals

Rightmarginals Total

Count 125 89 58 91 132 495% whole 58·4 46·1 81·0 33·0 52·3 52·5% burnt 13·6 11·2 13·8 14·3 15·1 13·7

Table 3(b). Front to back distribution of fully diagnostic carapace elements, showing frequencies of whole and burntspecimens

10 anteriorelements

24 centralelements

16 posteriorelements Total

Count 160 225 110 495% whole 56·3 44·0 64·5 52·5% burnt 14·4 13·7 12·7 13·7

996 C. G. Sampson

percentage values (Table 3(a)), and likewise from frontto back (Table 3(b)). The same outcome applies to theplastron (Table 4(a)). Predictably, limb bones aresomewhat more frequently charred than the shoulderand pelvis (Table 5(a)), but there is no difference incharring rates on the left or right side or on the frontgroup (15·9% burnt) versus the rear group (14·4%).Whatever causes the rear end of the tortoise to surviveless well than the front, roasting damage does notappear to be a factor.

Bowls and containersThese elements probably entered the fill as artefactsrather than foodwaste. Two carapace elements of H.boulengeri had their margins reduced by grinding andpolishing, and were clearly parts of tortoiseshell cups.They include a large m5 and a small m5. Also parts of

cups or containers were a medium c3, a small c3 and asmall hyoplastron, all with multiple scratches on theinside surfaces.

30

5b

0

0Percentage

Ph

ase

1

5a

4

2

10 20

214

70

136

193

378

308Charredshell

NIS

P

Uncharred

Charredskeletals

Figure 13. Cumulative percentages of charred shell and skeletalsthrough Phases 0–5b.

Table 4(a). Left and right distribution of fully diagnostic plastronelements, showing frequencies of whole and burnt specimens in eachgroup

All leftplastron

All rightplastron Entoplastron Total

Count 55 62 26 143% whole 40·0 32·3 65·4 38·6% burnt 21·8 19·4 15·4 18·3

Table 4(b). Front to back distribution of fully diagnostic plastronelements, showing frequencies of whole and burnt specimens

5 anteriorelements

4 posteriorelements Total

Count 91 52 143% whole 48·4 28·8 38·6% burnt 18·7 21·5 18·3

Table 5(a). Distribution of main classes of skeletal elements, with frequencies of whole and burnt specimens in eachclass

Cranial Pectoral Forelimb Axial Pelvic Hindlimb Total

Count 6 56 107 19 64 82 334% whole nd 41·1 20·6 nd 39·1 12·2 24·6% burnt nd 10·7 13·1 nd 12·5 15·8 12·3

Table 5(b). Distribution of left and right components of the main classes of skeletal elements, with frequencies ofwhole and burnt specimens in each category

Pectoral Forelimb Pelvic Hindlimb Total

Left Right Left Right Left Right Left Right Left Right

Count 17 30 43 53 23 33 30 27 113 143% whole nd 50·0 16·3 28·3 39·1 45·8 23·3 11·1 25·7 34·3% burnt nd 6·7 14·0 15·1 8·7 6·1 20·0 14·8 13·3 11·2

nd, not determined.

Tortoise Remains from a Later Stone Age Rock Shelter 997

Altogether 17 pieces of H. femoralis are from bowlfragments, including all the various marginals and anuchal, each with clear grinding and polish. Containerfragments include a hyoplastron, a c1, a c8 and an n4,all with heavily scratched interiors. There are two orthree small and one large element, while the others arefrom medium-size individuals.

It is noteworthy that two of the rare Psammobatestentorius elements are also bowl fragments. One is amedium nuchal and the other is a medium c3. Bowlfragments appear in Phase 2 and persist up to Phase5b. Most elements are widely scattered across theshelter floor, but small clusters of refitting H. femoralisbowl margins occur in Phase 5a and 5b.

DiscussionSpecies composition

There are more H. femoralis than H. boulengerithroughout the Haaskraal sequence, probably reflect-ing that Haaskraal is (and was) farther inside the rangeof H. femoralis, but closer to the easternmost edge ofthe natural range of H. boulengeri (Figure 1).

Fluctuations in the latter range are not forthcoming,and perhaps the site is deeper within the range ofH. boulengeri than is currently recorded. There weresignificant changes in plant cover during the past

millennium, as reflected in local pollen records (Scott &Bousman, 1990; Bousman & Scott, 1994). If these weresufficient in scale to alter the composition of the localmicromammal population (Avery, 1991), then theabsence of any response in the tortoise population isremarkable. Only further investigation will determinewhether they are more resistant than micromammals toveld changes at this scale.

The extreme paucity of the leopard tortoise G.pardalis is also noteworthy, given its modern-dayabundance in the surrounding landscape. Even moresurprising is the total absence of fully grown elements,since these giant adults are highly visible and yieldmore flesh. Leslie-Brooker (1987) notes the sameanomaly at Uniondale Shelter, but Hall (1990) reportsthe presence of adult bones, all extremely fragmented,in Edgehill Shelter. A schlepp effect is invoked toexplain the absence of shell. Leslie-Brooker suggeststhat predation on the eggs may have kept the numbersdown. Eggshell is present in Haaskraal fills, but itremains to be discovered whether this is from bird ortortoise eggs. Very heavy human predation on juvenileand young populations would prevent them growing tofull size, but this should be demonstrated by abundantremains in the rock shelters, an outcome clearly notsupported at Haaskraal. Another possibility for futureinvestigation is that G. pardalis has been only recentlyable to outcompete other species on the modern land-scape. Less open to rigorous testing is a scenario inwhich some taboo operated against killing the gianttortoises.

With the terrapin P. subrufa still commonly seen inthe adjacent Zoetvlei river channel, the extreme rarityof its remains in Haaskraal, only 1·7 km from thenearest long pool, is equally difficult to explain. Hall(1990), reporting a similar anomaly, invokes difficultyof capture, but concedes historic evidence to the con-trary. Although they disappear into the mud during thedry winter months, Haaskraal is not a winter-only site,as the amphibian remains make abundantly clear(Sampson, in press), so that season cannot be invokedto explain the absence.

The complete absence of C. angulata confirms thatHaaskraal is indeed outside its natural range. AlthoughC. angulata is found in the southern Karoo (Branch,1990), it may have been introduced farther north inrecent times in the form of pets which have escapedinto the surrounding countryside. If so, then it shouldbe absent from all pre-Colonial sites in the upperKaroo.

The paucity of tent tortoise P. tentorius, in spite ofHaaskraal’s position within the modern range of bothsubspecies, is also inexplicable. The same anomalousrarity was observed in Uniondale Shelter (Leslie-Brooker, 1987). Hewitt (1937) mentions that the youngof this species was devoured by ostriches to such anextent in one southeast Karoo district that it wasrendered almost extinct, but no obvious relationshipcan be seen in the Haaskraal data. Another possibility

0–5 g

5–10 g

10–15 g

15–20 g

20+ g

Weight of charcoal per c. 1500 cc of deposit

Phase 5b

Charred tortoise –large or medium

Charred tortoise –small or very small

Skeletal

1 m

Figure 14. Locations of the charred tortoise bone in Phase 5b inrelation to the hearths and surrounding charcoal scatters.

998 C. G. Sampson

requiring early investigation is the variability of P. t.verroxii skeletal morphology to assure that it does notoverlap with that of H. femoralis. Given that thisproject used only one element of P. t. verroxii forreference, there must be a residual doubt about poss-ible overlap. One consequence could be that someelements could be misclassified with the dominantH. femoralis.

Human versus non-human occupationNon-human detritus has been postulated to containhigh frequencies of skeletal elements, particularly ofvery small tortoises. Although modern control sampleshave not been studied, and field observations are stillneeded, it is intuitively reasonable that non-humanpredators could easily break the shell of very smalltortoises. They would eat out of the shell, swallowingmany skeletal parts while consuming the flesh. In thecase of birds, the skeletal material would be regurgi-tated while perching on the shelter floor. In the case ofsmall carnivores, whole or nearly whole baby tortoiseswould be carried into the shelter and selectivelydevoured, giving rise to higher frequencies of shell onthe shelter floor. Until modern control studies aredone, however, the identity of the non-humanpredator(s) cannot be determined.

Until that is done, a human cause for the rapid risein smaller tortoise skeletals in the historical levelscannot be entirely ruled out. Farm Bushmen may haveoverexploited the local tortoise population to such anextent that no adults survived. Roasting may havedestroyed their shells, a factor invoked to explain thepaucity of smaller shell elements lower in the sequence.

The same question hangs over a reported switch inthe proportions of amphibian remains. In Phase 5athere is a rapid increase in the thinly dispersed Karootoad Bufo gariepensis, a parallel increase in the numberof small individuals, and a patchy concentration awayfrom bone midden and towards the back of the shelter.These features contrast markedly with human food-waste in the pre-Contact layers which contain abun-dant remains of the much more easily procured giantbullfrog Pyxicephalus adspersus and the platannaXenopus laevis, both concentrated within the bonemiddens (Sampson, in press). There are almost nocharred amphibian remains. Near the surface, how-ever, is a patch of charred Bufo gariepensis bones whichwere certainly burnt in situ by a fire lit on top of them.This same process must have burned the small tortoisebones in Phase 5b. Overall, the amphibian data appearto support a non-human agent, but control studies arealso lacking for these data.

Roasting patternTortoises are difficult to kill, and least effort is involvedif they are roasted alive by placing them upside downin the fire. If so, then more of the carapace should be

burnt than the plastron, and still fewer skeletal partsshould be charred. This is not borne out by theHaaskraal data: in toto there are somewhat morecharred plastron fragments (20·5%) than charred cara-pace pieces (16·5%) and charred skeletal fragments arepredictably less (12·6%). Charring is not restricted tothe outside surfaces, and usually penetrated rightthrough the bone. The frequency of charring is evenlydistributed over all parts of the shell, suggestingthat they were placed in large fires. Recharring offoodwaste may also have contributed.

Summary and ConclusionsHaaskraal rock shelter was intermittently occupied byLater Stone Age hunter–gatherers from about 200until 1770 when the first European stockfarmersarrived. It remained in use for at least another centuryby farm Bushmen, but occupational intensity declinedrapidly towards the end. Throughout this time (exceptfor a five century hiatus between about 800 and 1300) the occupants deposited foodwaste around theedge of the main hearths, which gave rise to arc-shapedfaunal concentrations in the shelter fill. A numericallyprominent feature of these middens, tortoise remainsare found throughout the accumulation. There is noevidence that (like ostrich eggs) more tortoises wereeaten towards the end of the sequence, as the gamesupply diminished.

Four (possibly five) kinds of tortoise and a terrapincan be identified among these remains, in proportionswhich coincide with our still limited understanding oftheir modern frequencies in the surrounding veld. Mostcommon is the greater padloper H. femoralis, followedby the Karoo padloper H. boulengeri, with the tenttortoise P. tentorius and the leopard tortoise G. parda-lis merely present. Only a trace of the terrapin occurredin the sample. A trace of a fifth tortoise H. areolatuscannot be confirmed because present knowledge ofwithin-species osteological variability is so limited. Forthe same reason, P. tentorius cannot be confirmed tosubspecies, although modern distributional data leadone to expect most of this small sample to be P. t.verroxii.

The frequencies of these taxa do not vary signifi-cantly through the sequence, an outcome which con-flicts with expectations given what is known of thelocal pollen record and the parallel micromammalrecord. Evidently tortoises must be less sensitive toplant cover changes at the scale registered by theseother proxies.

On the surface of the shelter floor is a modest butimportant sample of relatively undamaged tortoisebones which must be non-human detritus, accumulatedafter the shelter was abandoned by humans. Its com-position is notably different from the human foodwastein that it contains mostly skeletal elements of small andvery small tortoises. They may have been regurgitated

Tortoise Remains from a Later Stone Age Rock Shelter 999

while raptors roosted on the shelter floor, but somecould also result from small carnivore habitation, or amix of both. These ‘‘markers’’ of non-human contribu-tion can be traced downwards through the sequence indiminishing frequencies, and are especially apparent inthe historical levels. Here, they are distributed awayfrom the main bone middens. Overall, this patternmust reflect a trend in which the shelter was unoccu-pied by humans for more and for longer spells, culmi-nating in its abandonment. No such pattern is visible,however, at the hiatus event between Phases 1 and 2.

The bulk of the tortoise sample is firmly embeddedin the bone middens. This, and the frequent occurrenceof charred pieces, makes it reasonably certain thatmost of this is human foodwaste, although someof it clearly derives from shells which were broughtto the site as bowls or containers. No patterns ofconcentrated damage or burning can be detected, how-ever, and the even distribution of charred elementsacross all parts of the carapace and plastron suggestunsystematic roasting and perhaps recharring offoodwaste.

Given its high visibility in surrounding veld, theshortage of G. pardalis in this sample and especially thecomplete absence of giant adult remains cannot beexplained. Perhaps its modern abundance is a recentaberration.

Although there is an obvious need for systematicobservations of avian predation in the region, thechronic shortage of an adequate range of referencematerial must also be addressed. In spite of theselacunae, the advantages of a complete element count,rather than selective study of specific elements, isdemonstrated: human and non-human components ofthe bone assemblage can be teased apart. Futureresearch should concentrate on developing markers fordetritus from small carnivores versus raptors, and fordetritus from different raptors. Until this is done, thepossibility that the rising percentage of smaller skel-etals in the historical levels reflect human over-cropping of the local tortoise population should notbe ruled out entirely. Further analysis of tortoisesamples from archaeological sites in the same regionare another clear requirement, and are in progress.

AcknowledgementsExcavations were directed by Tim Hart. Ina Plugseparated the bulk of the tortoise remains from themain faunal mass, assisted by Beatrix Sampson. Thelatter also assisted the author in two subsequent sweepsof the bulk fauna aimed at recovering the residue oftortoise fragments, and in double-checking the identi-fications. The reference specimens of tortoise skeletonsused in this project were generously provided by:Graham Avery, Division of Human Sciences, SouthAfrican Museum; Johan Binneman, Department ofArchaeology, Albany Museum; Bill Branch, Port

Elizabeth Museum; Denise Drinkrow, Division of LifeSciences, South African Museum; Peter Nilssen,Department of Archaeology, University of CapeTown; and by Royden Yates, University of CapeTown. The author wishes to thank all these colleaguesfor the loans, and for their advice and encouragement.Graham Avery’s comments on an earlier draft of thepaper helped greatly to improve the text. Aspects ofthis research were supported by the Foundation forResearch Development, Pretoria, and by the NationalScience Foundation, Washington, DC.

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